Protein Expression of PI3K/AKT/mTOR Pathway Targets Validated by Gene Expression and its Correlation with Prognosis in Canine Mammary Cancer

Mammary cancer is the main type of neoplasia in female dogs and is considered an adequate model for the biological and therapeutic study of cancer in women. The PIK3CA/AKT/mTOR pathway plays a central role in cellular homeostasis and is often dysregulated in cancer. The increased expression of PI3K protein in the literature is associated with a poor prognosis, and alterations in the PIK3CA gene can lead to changes in downstream pathways. Thus, the objective of this study was to validate the protein expression to confirm the gene expression of proteins belonging to the main pathway PI3K and PTEN, and their downstream pathways through ZEB1, ZEB2, HIF1A, VHL, CASP3 and PARP1 relating to prognosis in canine mammary cancer. For protein studies, the samples came from 58 female dogs with mammary neoplasia, immunohistochemistry was performed and its analysis by the histoscore method. For the genetic evaluation, the samples came from 13 patients, the DNA was extracted and the analysis for quantitative expression. Through immunohistochemistry, PI3K positivity was significantly associated with affected regional lymph node, distant metastasis, patients with HER2+, Triple Negative and Luminal B phenotypes, and the lowest survival rates. Through gene expression, we observed higher gene expression of ZEB2 and PARP1 both among patients who were alive and who died, which was not true for the expressions of PIK3CA and HIF1A. In conclusion, the data observed in this work are promising in the study of new molecular prognostic markers such as PI3K, ZEB2 and PARP1 for canine mammary cancer.

Presence of human breast cancer xenograft changes the diurnal profile of amino acids in mice

Human xenografts are extremely useful models to study the biology of human cancers and the effects of novel potential therapies. Deregulation of metabolism, including changes in amino acids (AAs), is a common characteristic of many human neoplasms. Plasma AAs undergo daily variations, driven by circadian endogenous and exogenous factors. We compared AAs concentration in triple negative breast cancer MDA-MB-231 cells and MCF10A non-tumorigenic immortalized breast epithelial cells. We also measured plasma AAs in mice bearing xenograft MDA-MB-231 and compared their levels with non-tumor-bearing control animals over 24 h. In vitro studies revealed that most of AAs were significantly different in MDA-MB-231 cells when compared with MCF10A. Plasma concentrations of 15 AAs were higher in cancer cells, two were lower and four were observed to shift across 24 h. In the in vivo setting, analysis showed that 12 out of 20 AAs varied significantly between tumor-bearing and non-tumor bearing mice. Noticeably, these metabolites peaked in the dark phase in non-tumor bearing mice, which corresponds to the active time of these animals. Conversely, in tumor-bearing mice, the peak time occurred during the light phase. In the early period of the light phase, these AAs were significantly higher in tumor-bearing animals, yet significantly lower in the middle of the light phase when compared with controls. This pilot study highlights the importance of well controlled experiments in studies involving plasma AAs in human breast cancer xenografts, in addition to emphasizing the need for more precise examination of exometabolomic changes using multiple time points.

Melatonin Treatment Combined with TGF-β Silencing Inhibits Epithelial- Mesenchymal Transition in CF41 Canine Mammary Cancer Cell Line

BACKGROUND

Mammary cancer is the most prevalent type of cancer in female dogs. The main cause of mortality is the occurrence of metastasis. The metastatic process is complex and involves the Epithelial- Mesenchymal Transition (EMT), which can be activated by Transforming Growth Factor beta (TGF-β) and involves changes in cellular phenotype, as well as, in the expression of proteins such as E-cadherin, N-cadherin, vimentin and claudin-7. Melatonin is a hormone with oncostatic and anti-metastatic properties and appears to participate in the TGF-β pathway. Thus, the present work aimed to evaluate the expression of EMT markers, E-cadherin, N-cadherin, vimentin and claudin-7, as well as, the cell migration of the canine mammary cancer cell line, CF41, after treatment with melatonin and TGF-β silencing.

METHODS

Canine mammary cancer cell line, CF41, was cultured and characterized in relation to markers ER, PR and HER2. Cell line CF41 with reducing expression level of TGF-βwas performed according to Leonel et al. (2017). Expression of the protein E-caderin, N-cadherin, vimentin and claudin-7 was evaluated by immunocytochemistry and quantified by optical densitometry. The analysis of cell migration was performed in transwell chambers with 8μM pore size membrane.

RESULTS

CF41 cells present a triple negative phenotype, which is an aggressive phenotype. Immunocytochemistry staining showed increased expression of E-caderin and claudin-7 (P˂0.05) and decreased expression of N-cadherin and vimentin (P˂0.05) in CF41 cells after treatment with 1mM melatonin and TGF-β silencing. Moreover, treatment with melatonin and TGF-β silencing was able to reduce migration in cell line CF41 (P˂0.05).

CONCLUSION

Our data suggests that therapies combining TGF- β1 silencing and melatonin may be effective in suppressing the process of EMT, corroborating the hypothesis that melatonin acts on the TGF-β1 pathway and can reduce the metastatic potential of CF41 cells. This is so far the first study that reports melatonin treatment in CF41 cells with TGF-β1 silencing and its effect on EMT. Thus, further studies are needed to confirm this hypothesis.

Global gene expression profile in canine mammary carcinomas

Mammary gland tumors are a heterogeneous group of neoplastic diseases. Genetic studies make it possible to determine genetic profiles and identify new molecular markers. The aim of the study was to evaluate the gene expression profile of canine mammary carcinomas and identify potential prognostic markers. Twelve mammary cancer samples from bitches were collected for the evaluation of global gene expression. Microarray assays were performed using commercial kits. Statistical analysis of the microarray was done using moderate t-statistic and adjusted using the Benjamini and Hochberg procedure. Differential connectivity analysis was also performed. Enrichment analyses were conducted using WebGestalt. P-values were calculated using hypergeometric statistics and adjusted using the Benjamini and Hochberg procedure. The HYAL-1 gene was validated using quantitative PCR (qPCR). There were 878 upregulated genes and 821 downregulated genes in the neoplasms studied. Enrichment analysis (individual analysis) identified the HYAL-1 gene as a potential marker of tumorigenesis and tumor recurrence. Differential connectivity analysis demonstrated 262 differentially connected genes.

Melatonin Differentially Modulates NF-кB Expression in Breast and Liver Cancer Cells

BACKGROUND

NF-kB (nuclear factor kappa B) is a transcription factor composed of two subunits, p50 and p65, which plays a key role in the inflammatory process. Melatonin has oncostatic, antiangiogenic and antimetastatic properties, and some recent studies have indicated an inhibitory effect of melatonin on NF-kB in some types of cancer. This work aims to investigate the effects of melatonin treatment on the expression of NFkB in breast and liver cancer models.

METHOD

The breast cancer xenographic model was performed using female Balb/c nude athymic mice injected with MDA-MB-231 cells. The animals were treated with 40 mg/Kg of melatonin for 21 days. Volume of the tumors was measured with a digital caliper. Hepatocarcinoma model was developed by using the HepG2 cells in vitro, treated with 1 mM melatonin for 24 h. The expression of NF-kB protein was verified by immunohistochemistry and immunocytochemistry and quantified by optical densitometry, in vivo study and in vitro study, respectively. NF-kB gene expression was performed by quantitative RT-PCR.

RESULTS

The breast cancer xenografts nude mice treated with melatonin showed reduced tumor size (P=0.0022). There was a decrease in NF-kB protein staining (P=0.0027) and gene expression (P=0.0185) in mice treated with melatonin. The opposite results were observed for the hepatocarcinoma model. HepG2 cells treated with melatonin showed an increase in the NF-kB immunostaining when compared to control cells (P=0.0042).

CONCLUSION

Our results indicated that the treatment with melatonin was able to decrease both gene and protein expressions of NF-kB in breast cancer cells and, conversely, increase the transcription factor protein expression in hepatocarcinoma cells. These data highlighted a double role in the expression of NF-kB, depending on the cell type. Further studies are needed to better elucidate the action of melatonin in NF-kB, since this transcription factor acts on different signaling pathways that are fundamental for carcinogenesis.

Multiparametric MRI and Coregistered Histology Identify Tumor Habitats in Breast Cancer Mouse Models

It is well-recognized that solid tumors are genomically, anatomically, and physiologically heterogeneous. In general, more heterogeneous tumors have poorer outcomes, likely due to the increased probability of harboring therapy-resistant cells and regions. It is hypothesized that the genomic and physiologic heterogeneity are related, because physiologically distinct regions will exert variable selection pressures leading to the outgrowth of clones with variable genomic/proteomic profiles. To investigate this, methods must be in place to interrogate and define, at the microscopic scale, the cytotypes that exist within physiologically distinct subregions ("habitats") that are present at mesoscopic scales. MRI provides a noninvasive approach to interrogate physiologically distinct local environments, due to the biophysical principles that govern MRI signal generation. Here, we interrogate different physiologic parameters, such as perfusion, cell density, and edema, using multiparametric MRI (mpMRI). Signals from six different acquisition schema were combined voxel-by-voxel into four clusters identified using a Gaussian mixture model. These were compared with histologic and IHC characterizations of sections that were coregistered using MRI-guided 3D printed tumor molds. Specifically, we identified a specific set of MRI parameters to classify viable-normoxic, viable-hypoxic, nonviable-hypoxic, and nonviable-normoxic tissue types within orthotopic 4T1 and MDA-MB-231 breast tumors. This is the first coregistered study to show that mpMRI can be used to define physiologically distinct tumor habitats within breast tumor models. SIGNIFICANCE: This study demonstrates that noninvasive imaging metrics can be used to distinguish subregions within heterogeneous tumors with histopathologic correlation.

Abstract B85: Plasmatic levels of arginine, its precursors and acylcarnitines affected by melatonin at specific time of the day

The circadian rhythm regulates almost the whole metabolism modulating the concentration of various circulating substances through the clear and dark variation. Melatonin is the main mediator of this bidimensional flow, although studies have shown that metabolic diseases like cancer have already been associated to the imbalance of this rhythm. Actually, melatonin has several anticancer effects extensively described in the literature and proved by our group. Nowadays, metabolomics analysis has been used in cancer science to provide a comprehensive profile of the metabolic changes seeking to uncover characteristics about the tumor behavior. Studies in this field have discovered a lot of new biochemical pathways involved in the homeostasis and disorders. It is noticeable that important tumor features are regulated by essential molecules involved in bioenergy and cell structure, likewise amino acids and fatty acids. Therefore, the comprehension of specific metabolites that may be modulated by the exogenous melatonin is essential to verify its use as cancer adjuvant treatment. The aim of this study was to evaluate the metabolic profile in breast cancer xenograft model under treatment with melatonin across the circadian variation. We used 160 female Balb/c nude athymic mice separated into four groups: tumor/melatonin, tumor/vehicle, nontumor/melatonin, and nontumor/vehicle. The tumor model was developed by implantation of 3 x 106 triple-negative human breast cancer cells (MDA-MB-231) in the mammary fat pad. All the animals received 100 ul of solution by intraperitoneal injection (IP) for five days a week during 21 days. Treated groups received 40 mg/kg of melatonin and nontreated group only received vehicle solution. Blood sample were collected every 3 hours during 24 hours and the plasma was extracted for liquid chromatography and mass spectrometry (LC-MS) analysis using the Absolute IDQ p180 Kit (BioCrates). Our Orthogonal Partial Least Squares (OPLS) analysis showed evident separation of the metabolic profile not only because of the circadian cycle, but also because of the melatonin treatment. By looking for specific pathways we found that tumor/vehicle group showed significant increases in the plasmatic levels of arginine, citrulline, and ornithine, specifically at 6 am and 9 am (p < 0.001). Arginine metabolism is well known to be strongly involved in the initial phase of tumor growth (Lind, 2004; HU et al., 2016), favoring the synthesis of molecules very important for various biologic processes of normal and tumor cells. Beyond the aminoacids we also found significantly raised levels of medium- and long-chain acylcarnitines, specifically at 3 pm (p < 0.001). Acylcarnitines are mainly responsible for the fatty acid metabolism, which is a fundamental energy source. Synthesis of fatty acids is required for membrane synthesis and therefore for cell growth and proliferation. Our results show that tumor-bearing animals treated with melatonin have shown reduced plasma levels of these metabolites, achieving the same levels of non-tumor bearing animals. In summary, this work reveals a strong relationship between the metabolic profile and the entire circadian variation as well as the fact that exogenous melatonin can regulate the metabolites' concentration. This preclinical trial showed increased plasmatic levels of arginine, its precursors and acylcarnitines at specific time of the day, and the treatment with melatonin is able to decrease the serum levels of these metabolites. Thus our results corroborate the literature which characterizes these metabolites as cancer biomarkers and increasingly allows the use of melatonin as an adjuvant therapy for breast cancer.

Citation Format: Rubens Paula Junior, Nathália Martins Sonehara, Debora A. P. C. Zuccari. Plasmatic levels of arginine, its precursors and acylcarnitines affected by melatonin at specific time of the day [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr B85.

Melatonin and IL-25 modulate apoptosis and angiogenesis mediators in metastatic (CF-41) and non-metastatic (CMT-U229) canine mammary tumour cells

BACKGROUND

Melatonin has oncostatic actions and IL-25 is active in inflammatory processes that induce apoptosis in tumor cells AIM: The aim of this study was to evaluate melatonin and IL-25 in metastatic (CF-41) and non-metastatic (CMT-U229) canine mammary tumor cells cultured as monolayers and tridimensional structures.

MATERIALS AND METHODS

The cells were treated with melatonin, IL-25 and IL-17B silencing gene and performed cell viability, gene and protein expression of caspase-3 and VEGFA (Vascular endothelial growth factor A) and an apoptosis membrane protein array.

RESULTS

Treatment with 1 mM of melatonin reduced cell viability of both tumor cell lines, all treatments alone and combined significantly increased caspase-3 cleaved and proteins involved in the apoptotic pathway and reduced pro-angiogenic VEGFA, confirming the effectiveness of these potential promising treatments.

CONCLUSION

This is the first study evaluating the potential use of these strategies in CF-41 and CMT-U229 cell lines and together encourages subsequent in vitro and in vivo studies for further exploration of clinical applications.

Abstract P1-05-28: Melatonin treatment: A transcriptomic networks in a xenograft model of breast cancer

Melatonin is a hormone produced by the pineal gland and has been shown different antitumor effects, as immunomodulatory, antioxidant, pro-apoptotic, anti-proliferative, antimetastatic and antiangiogenic, however, the pathways by which melatonin exerts its action need to be identified. Thus, the aims of this study were to perform the transcriptome analysis to evaluate the pathways of melatonin action in triple-negative breast cancer. Triple-negative breast cancer cells (MDA-MB-231) were injected into the mammary gland of the athymic nude mice (n=10), which were treated with melatonin (40 mg/kg) or vehicle during 21 days. RNA-Seq libraries were created using Truseq RNA-Seq Library Prep Kit v2. The experiment was paired-end with 100nt read length, performed on the Illumina HiSeq2500 sequencer, producing about 30 million reads per library. To differentiate human and mouse expression, the alignment was performed to filter out mouse-like reads before mapping to the human reference and vice versa, and data were mapped against human (GRCh37/hg19) and mouse (NCBI37/mm9) genomes separately, using the TopHat software. The HTSeq was employed for analyses of read counts and DESeq2 was used to identify genes differentially expressed between melatonin treated and control tumors. Differentially expressed genes (DEGs) were identified based on a false discovery rate (FDR) q-value threshold of less than 0.05. Also, we applied Weighted Gene Co-expression Network Analysis (WGCNA) to detect clusters of highly co-expressed genes (modules). Results showed that animals treated with melatonin had smaller tumors volume than controls (p<0.05). RNA-Seq data showed that 57.24% of reads mapped uniquely to human, 29.66% reads in mouse and 11% reads mapping to both human and mouse genomes. In human tumor cells, there was no DEGs between melatonin treated and control group (adjP>0.05). In mouse cells, which represent the tumor microenvironment, there were 34 DEGs between animals treated with melatonin and controls (adjP<0.05). In tumors cells, we detected 714 differentially co-expressed genes (IKdiffI>0.6), which were functionally enriched for GO terms like lipid metabolic process, response to drug, oxidoreductase activity and PPAR signaling (adjP<0.1). Also, we identified 3 gene modules strongly associated with melatonin treatment, which were related with metabolic pathways (adjP<0.1). In mouse cells, were detected 1345 differentially co-expressed genes, which were enriched for signaling pathways like Wnt receptor, Hedgehog and TGF-beta (adjP<0.1). There were 3 gene modules strongly associated with melatonin treatment, which are enriched for regulation of translation and cell cycle, immune system process and T cell differentiation, regulation of action cytoskeleton and ErbB signaling pathway (adjP<0.1). Also, potential regulator genes for melatonin treatment were detected by generating clusters of co-expressed genes and individual analysis confirms these results. Transcriptomic network analysis coupled with other results showed that melatonin treatment controls the tumor growth, acting especially by metabolic pathways in tumor cells and modulating the tumor microenvironment.

Citation Format: Jardim-Perassi BV, Sonehara NM, de Paula-Junior R, Chammas R, Coutinho LL, Reis Júnior O, Alexandre PA, Fukumasu H, Zuccari DAPC. Melatonin treatment: A transcriptomic networks in a xenograft model of breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-05-28.

HET0016, a selective inhibitor of 20-HETE synthesis, decreases pro-angiogenic factors and inhibits growth of triple negative breast cancer in mice

A selective inhibitor of 20-HETE synthesis, HET0016, has been reported to inhibit angiogenesis. 20-HETE has been known as a second mitogenic messenger of angiogenesis inducing growth factors. HET0016 effects were analyzed on MDA-MB-231 derived breast cancer in mouse and invitro cell line. MDA-MB-231 tumor cells were implanted in animals’ right flank and randomly assigned to early (1 and 2), starting treatments on day 0, or delayed groups (3 and 4) on day 8 after implantation of tumor. Animals received HET0016 (10 mg/kg) treatment via intraperitoneal injection for 5 days/week for either 3 or 4 weeks. Control group received vehicle treatment. Tumor sizes were measured on days 7, 14, 21, and 28 and the animals were euthanized on day 22 and 29. Proteins were extracted from the whole tumor and from cells treated with 10 µM HET0016 for 4 and 24 hrs. Protein array kits of 20 different cytokines/factors were used. ELISA was performed to observe the HIF-1α and MMP-2 protein expression. Other markers were confirmed by IHC. HET0016 significantly inhibited tumor growth in all treatment groups at all-time points compared to control (p<0.05). Tumor growth was completely inhibited on three of ten animals on early treatment group. Treatment groups showed significantly lower expression of pro-angiogenic factors compared to control at 21 days; however, there was no significant difference in HIF-1α expression after treatments. Similar results were found invitro at 24 hrs of HET0016 treatment. After 28 days, significant increase of angiogenin, angiopoietin-1/2, EGF-R and IGF-1 pro-angiogenic factors were found (p<0.05) compared to control, as well as an higher intensity of all factors were found when compared to that of 21 day’s data, suggesting a treatment resistance. HET0016 inhibited tumor growth by reducing expression of different set of pro-angiogenic factors; however, a resistance to treatment seemed to happen after 21 days.

Geoffroy's side-necked turtle [Phrynops geoffroanus (Schweigger, 1812), Testudines: Chelidae] as a model for evolutionary ecotoxicology: relationship between environmental contamination, conditions and genetic variability

The objective of this study was to evaluate the role of human activity factors, such as environmental contamination and habitat changes, as drivers for changing the physiological, biochemical, and genetic diversity of Geoffroy's side-necked turtle populations in one of the most impacted watersheds in southeastern Brazil. The impact of chemical and organic contamination was determined by ecotoxicological analyses to assess the action of some of the major components involved in protection against oxidative stress, phase I and II detoxification metabolism, and antioxidant capacity. The results indicated the influence of domestic and industrial effluents on detoxification metabolism and oxidative stress. However, in spite of increased activity and effect of EROD (CYP1A1) and glutathione S-transferase (GST) activity, GST average values in the urban area agreed with those expected for hypoxic conditions according to the literature. This observation suggests that increased GST in response to ROS production due to the presence of pollutants increases the antioxidant defense network, controlling the oxidative damage caused by hypoxia and reperfusion. To determine the conditions that are reflected in individual ability (fitness), we evaluated the mathematical relationship between weight and length, and found that changes in body shape and weight increase, allowing inferences about animal health and welfare. The data obtained indicate differences in conditions that are associated with the area, but also with sex and reproductive period, and contamination gradient, indicating a strong influence of environmental stressors on the physiology of the specimens. The evaluation of genetic structure among populations of Preto River and Felicidade Stream, based on microsatellites, demonstrated that there was no genetic differentiation, due to extensive gene flow between the areas and high genetic diversity. However, after analysis of intrapopulation structure, we observed the existence of five genetic groups that reflected changes in habitat created by damming and siltation, which initiate separation processes (barriers) between sub-populations. The relationship between the data obtained for biochemical parameters, condition factors and genetic diversity was analyzed by heterozygosity-fitness correlation. The negative relationship observed may be explained by the profile of structural and ecological changes in the populations studied, indicating the important influence of humans on the biology of natural populations. Therefore, Phrynops geoffroanus shows adaptation to environmental contamination, and ecological changes and possible loss of habitat are altering the genetic diversity of the populations studied. This is the first study evaluating all these aspects of P. geoffroanus simultaneously in natural populations in Brazil, using this species as a model.

Abstract C30: Laminin-5 expression in breast cancer culture cells after chemotherapic exposure

Introduction: Laminin-5, a large heterotrimeric glycoprotein consisting of an alpha 3, beta 3, and gamma 2 chain, is a component of epithelial cell basement membranes that functions as a ligand of the alpha 3 beta 1 and alpha 6 beta 4 integrins to regulate cell adhesion, migration, and morphogenesis. Laminins also regulate cellular movement, growth and differentiation, induce inflammatory cells and integrate the extracellular matrix to epithelia. It is suspect to be a tumor suppressor gene in breast cancer resulting in inhibition of tumor metastasis. In contrast, recent studies describe that as a modify and metastatic gene. The importance of laminin-5 in the development of a variety of cancers makes it an attractive target for cancer therapeutics. This study was conducted to determine the laminin-5 expression after exposure to routine chemotherapy in breast carcinoma culture cells. The concept is that laminin-5 expression change after doxorubicin exposure. Studying chemotherapy-induced gene expression changes in vitro could provide insights into mechanisms of chemotherapy resistance.

Material and Methods: Doxorubicin exposure was performed on tumor tissue obtained from ten newly diagnosed carcinoma. The gene expression was determined before and after doxorubicin aggression. PCR amplifications were performed using a 7500 Fast Real-Time PCR System (Applied Biosystems). The gene expression stability over different samples was analyzed using the geNorm software.

Results: The cells were cultured for about 30 days. Then their origin was proof by immunohistochemical procedure using citoqueratin and vimentin. After that, the curve of growth was made after exposure to doxorubicin. There was distinct expression of laminin 5 in breast cancer culture cells. When the molecular study was concern there were statistical correlation between the gene expression and the drug resistance.

Discussion and Conclusion: Laminin-5 has abnormal expression and its integrin receptors are hallmark of certain tumor types and are believed to promote invasion of colon, breast and skin cancer cells. In invasive cancers, laminins usually become discontinuous or absent around tumor foci, which is attributed to either increased degradation or reduced synthesis. The importance of laminin-5 in the development of a variety of cancers makes it an attractive target for cancer therapeutics. However, laminin-5 based cancer therapies are not without their problems since treatments of necessity must target tumor laminin-5 but not laminin-5 in normal tissues since the latter is essential for maintaining tissue integrity. Future development of new reagents that inhibit the ability of laminin-5 to drive tumor growth and/or dissemination will be greatly facilitated once we better understand not only the precise regulation of laminin-5 proteolytic processing but also the different signaling cascades regulated by laminin-5 in normal versus tumor cells. Gene expression alterations of breast cancer were specific to doxorubicin treatment, and yielded mechanistic insights into resistance to the drug. Gene expression analysis provides more global perspectives on resistance pathways that could be exploited for therapeutic selection. Consideration of these factors should be incorporated in clinical practice after appropriate validation studies are performed to avoid confounding results, making them true prognostic and predictive factors.

Financing agency: FAPESP

Citation Information: Cancer Res 2009;69(23 Suppl):C30.

Immunocytochemical study of Ki-67 as a prognostic marker in canine mammary neoplasia

BACKGROUND

Canine mammary tumors are challenging for clinicians and pathologists because of complex histologic classification, low specificity of cytologic diagnosis, and unpredictable biological behavior. In histologic specimens, expression of tumor proliferation marker Ki-67, a nuclear nonhistone protein, has been shown to have prognostic value for canine mammary tumors and to correlate with malignancy and low survival rates.

OBJECTIVE

The objective of this study was to measure the proliferation index of canine mammary tumors by immunochemical detection of Ki-67 in cytologic specimens and to determine its relationship to clinical and pathologic variables and patient outcome.

METHODS

Spontaneous mammary tumors from 31 female dogs were surgically excised. Imprint specimens for cytologic evaluation were wet-fixed in ethanol; histologic specimens were prepared routinely. Immunostaining was performed with the PH 177 monoclonal antibody against Ki-67; proliferation index was graded from negative to +++. Dogs were followed for 18 months. Multivariate logistic regression analysis was used to determine correlations between immunocytochemical results, tumor and clinical variables, and patient outcome.

RESULTS

Ki-67 proliferation indices in cytologic specimens were significantly lower for nonmalignant tumors than for malignant tumors. High index values of Ki-67 were positively correlated with metastasis, death from neoplasia, low disease-free survival rates, and low overall survival rate. With the exception of 4 specimens for which cellularity was insufficient, positive expression of Ki-67 in cytologic specimens correlated with that of histologic specimens.

CONCLUSIONS

The prognostic value of the Ki-67 index in canine mammary tumors by using wet-fixed cytology imprint specimens was similar to that observed previously for histologic specimens. Immunocytochemical detection of Ki-67 could improve the accuracy and value of cytology by providing safe and rapid information about malignancy and patient outcome.